1. Field of the Invention
The present invention relates to a sealing method in which when a seal portion of a packaging container is sealed, a specific part serving as an inspective object is formed so that it can be used for inspection of the sealed portion, and also relates to heat-treating plates for use in the sealing method. Further, the present invention relates to an inspection apparatus and method for inspecting the inspective object. In addition, the present invention relates to an automatic filling and packaging system having such an inspection apparatus.
2. Discussion of Related Art
As packaging containers for foods and the like, bags are widely used which are made of a packaging material formed from a stack of a plurality of thin synthetic resin films in which the innermost layer is made of a thermoweldable resin material, e.g. polyethylene. The operation of filling a food or other material into such a bag is automated. That is, the mouth portion of the bag is opened, and the material to be packed is filled into the bag. After necessary treatment, e.g. deaeration, has been performed, the bag mouth portion is pressed between a pair of hot plates or the like to weld together the mutually opposing innermost layers, thereby sealing the mouth portion of the bag. Recently, use has been made of spouted packaging containers that are convenient for storing a beverage, e.g. a sports drink or juice, in a portable fashion. Sealing between the spout and the container body is effected mostly by welding.
Incidentally, there has heretofore been provided no method of accurately judging the sealing quality of the sealed portion of such a packaging container, which has been sealed by thermal welding. In general, the inspection for the sealing quality is performed by visual observation, which lacks reliability. With the conventional sealing method, a specific part capable of representatively indicating the sealing condition of the sealed portion is not formed. To perform an inspection for the sealing quality, the whole sealed portion needs to be inspected. Accordingly, a great deal of time is required for the inspection, and it is likely that defectives may be overlooked.
The present invention was made in view of the above-described problems associated with the prior art. Accordingly, an object of the present invention is to make it possible to accurately inspect a sealed portion of a packaging container formed of a resin packaging material, which is sealed by utilizing fusion bonding of the packaging material. More specifically, an object of the present invention is to provide a sealing method wherein when a seal portion of a packaging container is sealed, an inspective object capable of representatively indicating the sealing condition of the sealed portion is formed, and also provide heat-treating plates for use in the sealing method. Another object of the present invention is to provide an inspection method and apparatus particularly suitable for inspecting an inspective object formed as stated above.
To attain the above-described objects, the present invention provides a sealing method in which a welding layer constituting the innermost layer of the base material of a packaging container is melted at a seal portion defined along the edge of an opening portion to be sealed of the packaging container. A part of the melt from the welding layer is allowed to flow out from the edge of the opening portion at a predetermined position along the edge and solidified to form an efflux layer serving as an inspective object.
In addition, the present invention provides a pair of heat-treating plates suitable for use in the above-described sealing method. The heat-treating plates press an opening portion of a packaging container from both sides to seal the opening portion and, at the same time, to form the above-described efflux layer as an inspective object. The heat-treating plates have respective welding portion-pressing portions facing each other to press a welding portion of the packaging container defined at a predetermined distance from the edge of the opening portion. The heat-treating plates further have respective extension-pressing portions facing each other to press an extension defined at a predetermined position along the edge of the opening portion to extend with a predetermined width from the welding portion to the edge. Preferably, the heat-treating plates are provided as cooling plates for cooling the welding portion melted by hot plates.
The inspection of the sealed portion according to the present invention is performed as follows. An image of an imaging subject including at least a part of the sealed portion and its vicinities is taken. At least a part of the taken image is defined as an inspection region. The image of the inspection region is subjected to predetermined image processing to calculate data concerning an efflux layer formed outside the sealed portion by the melted material flowing out of the sealed portion. The calculated data is compared with a preset condition for judgment to judge the sealing quality of the sealed portion.
To perform the above-described inspection, an apparatus for inspecting the sealed portion according to the present invention includes an imaging device, and a controller including a central control unit, a defective area setting unit, and a sealing quality judging unit. The imaging device takes an image of at least a part of the sealed portion and its vicinities. The central control unit controls the sealed portion inspection apparatus. Further, the central control unit captures the image taken with the imaging device, defines an inspection region including at least a part of the taken image in accordance with the inspection conditions, divides the inspection region into a plurality of pixels of a predetermined size, and judges whether or not each pixel located outside the sealed portion is filled with the efflux layer formed by the melted material flowing out of the sealed portion. The defective area setting unit sets inspection conditions and a criterion for judgment of the sealing quality. The sealing quality judging unit compares the result of the judgment made by the central control unit with the criterion for judgment to judge the sealing quality.
Preferably, the position of the inspection region is controlled in accordance with the position of the imaging subject within the field of view of the imaging device.
Other objects and advantages of the present invention will become apparent from the following detailed description of illustrated embodiments of the invention.